Nested virtualization is guest operating system is itself a hypervisor that virtualizes not just processors and memory but also storage, networking hardware assists, and other resources. The VM hypervisor represents the first implementation of practical nested virtualization with hardware assists for performance. There are a number of hypervisors support nested virtualization though not as efficiently as they could. The Linux KVM supports nesting on recent virtualization-enabled processors. How to enable Nested Virtualization OpenStack cloud ?

You need to the vmx cpu flag to be enabled inside your instances.

How to enable Nested virtualization in OpenStack Cloud

I have installed OpenStack using PackStack in our physical server. After successfully installed, verified that the setup is working fine.

We need to enable nested virtualization OpenStack cloud at the kernel level: